Titanium dioxide slurries

Abstract

Improved methods for producing titanium dioxide slurries. The output from a micronizer is passed through a condenser to condense the steam and form an aqueous slurry of titanium dioxide, which can in most cases then be further concentrated as desired or which can be sold or used without further concentration, instead of passing the micronizer output to apparatus for separating the TiO2 from the steam, as is currently practiced in the art. The resultant slurry from the condenser is in a further refinement preferably sent to an agitated storage tank together with dispersant and anti-settling compounds to aid in preventing settling of the titanium dioxide solids out of the slurry. To help facilitate condensation of the steam / pigment mixture sent to the condenser, a portion of the condensed slurry is in yet a further refinement pumped from the slurry storage tank to a heat exchanger. The output from the heat exchanger is then fed to the condenser to facilitate the condensing of the steam in the condenser. The temperature and volume (flow) of cooled condensate to the condenser are set to match the amount of steam and its temperature so as to ensure that substantially all of the steam and contained pigment are collected from the condenser.

Description

FIELD OF THE INVENTION [0001] The present invention generally relates to slurries of titanium dioxide. More specifically, the present invention relates to concentrated slurries of titanium dioxide and methods for producing concentrated slurries of titanium dioxide. BACKGROUND [0002] Titanium dioxide (“TiO2”) has many known uses in industry. For example, TiO2 is used as a pigment for many paints. It is also used in other applications such as paper making, plastics applications and coating compositions. [0003] Methods for producing TiO2 are also known in the art. TiO2 is generally produced by hydrolyzing an aqueous solution of titanium sulfate and calcining the hydrolyzate at about 750-1000° C., or oxidizing titanium tetrachloride (“TiCl4”) at elevated temperatures followed by cooling at temperatures below about 600° C. The TiO2 thus prepared is dry or wet ground and then dry milled. One method of dry milling is accomplished by utilizing a micronizer (also sometimes referred to as a f...

AI Technical Summary

Benefits of technology

[0022] The second example was carried out to serve as a control and to demonstrate the advantage of the present invention over existing art. Using an identically-sized micronizer to that used in Example 1, a quantity of dry micronized pigment was generated. The micronizer arrangement for this second example was such that it allowed for the micronized pigment to be separated from the superheated steam without any increase in the moisture content of the finished pigment, in keeping with the existing art methods. Separation of the pigment from the steam was for this Comparative Example achieved through the use of a series of cyclones providing approximately 85-90% recovery of the pigment fed to the micronizer. Steam and pigment flow-rates along with steam temperature were identical to those used in Example 1. The pigment used was the same starting pigment also described in Example 1.

over existing art. Using an identically-sized micronizer to that used in

Problems solved by technology

While this results in some initial dilution of the condensate, the amount added is small and would not be expected to significantly impact the overall operation.

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